s390/dumpstack: fix call chain walking
authorHeiko Carstens <heiko.carstens@de.ibm.com>
Thu, 14 Mar 2013 12:44:25 +0000 (13:44 +0100)
committerMartin Schwidefsky <schwidefsky@de.ibm.com>
Wed, 17 Apr 2013 12:07:28 +0000 (14:07 +0200)
dumpstack() did not always print a sane callchain when being called.
The reason is that show_trace() accessed register 15 directly to get
the current stack pointer and passed that pointer to __show_trace()
which expects a valid stack frame pointer as argument.
However due to tail call optimization the stack frame may not exist
anymore when __show_trace() gets called and therefore an invalid
stack frame pointer gets passed.
To prevent that disable tail call optimization for call chain walking
functions.
So move all the show_* functions to a dumpstack.c file like other
architectures have it already and add a -fno-optimize-sibling-calls
compile flag to both dumpstack.c and stacktrace.c to prevent tail
call optimization.

Fixes callchains that looked e.g. like this:

[   12.868258] Call Trace:
[   12.868262] ([<0000000000008000>] 0x8000)

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
arch/s390/kernel/Makefile
arch/s390/kernel/dumpstack.c [new file with mode: 0644]
arch/s390/kernel/traps.c

index 2ac311ef5c9b11a3b37aa4f5586a240aa14679a6..1386fcaf4ef6c7854838df1563604bca1d74603a 100644 (file)
@@ -13,6 +13,14 @@ endif
 #
 CFLAGS_smp.o   := -Wno-nonnull
 
+#
+# Disable tailcall optimizations for stack / callchain walking functions
+# since this might generate broken code when accessing register 15 and
+# passing its content to other functions.
+#
+CFLAGS_stacktrace.o    += -fno-optimize-sibling-calls
+CFLAGS_dumpstack.o     += -fno-optimize-sibling-calls
+
 #
 # Pass UTS_MACHINE for user_regset definition
 #
@@ -20,10 +28,11 @@ CFLAGS_ptrace.o             += -DUTS_MACHINE='"$(UTS_MACHINE)"'
 
 CFLAGS_sysinfo.o += -Iinclude/math-emu -Iarch/s390/math-emu -w
 
-obj-y  :=  bitmap.o traps.o time.o process.o base.o early.o setup.o vtime.o \
-           processor.o sys_s390.o ptrace.o signal.o cpcmd.o ebcdic.o nmi.o \
-           debug.o irq.o ipl.o dis.o diag.o mem_detect.o sclp.o vdso.o \
-           sysinfo.o jump_label.o lgr.o os_info.o machine_kexec.o pgm_check.o
+obj-y  := bitmap.o traps.o time.o process.o base.o early.o setup.o vtime.o
+obj-y  += processor.o sys_s390.o ptrace.o signal.o cpcmd.o ebcdic.o nmi.o
+obj-y  += debug.o irq.o ipl.o dis.o diag.o mem_detect.o sclp.o vdso.o
+obj-y  += sysinfo.o jump_label.o lgr.o os_info.o machine_kexec.o pgm_check.o
+obj-y  += dumpstack.o
 
 obj-y  += $(if $(CONFIG_64BIT),entry64.o,entry.o)
 obj-y  += $(if $(CONFIG_64BIT),reipl64.o,reipl.o)
diff --git a/arch/s390/kernel/dumpstack.c b/arch/s390/kernel/dumpstack.c
new file mode 100644 (file)
index 0000000..03dce39
--- /dev/null
@@ -0,0 +1,236 @@
+/*
+ * Stack dumping functions
+ *
+ *  Copyright IBM Corp. 1999, 2013
+ */
+
+#include <linux/kallsyms.h>
+#include <linux/hardirq.h>
+#include <linux/kprobes.h>
+#include <linux/utsname.h>
+#include <linux/export.h>
+#include <linux/kdebug.h>
+#include <linux/ptrace.h>
+#include <linux/module.h>
+#include <linux/sched.h>
+#include <asm/processor.h>
+#include <asm/debug.h>
+#include <asm/ipl.h>
+
+#ifndef CONFIG_64BIT
+#define LONG "%08lx "
+#define FOURLONG "%08lx %08lx %08lx %08lx\n"
+static int kstack_depth_to_print = 12;
+#else /* CONFIG_64BIT */
+#define LONG "%016lx "
+#define FOURLONG "%016lx %016lx %016lx %016lx\n"
+static int kstack_depth_to_print = 20;
+#endif /* CONFIG_64BIT */
+
+/*
+ * For show_trace we have tree different stack to consider:
+ *   - the panic stack which is used if the kernel stack has overflown
+ *   - the asynchronous interrupt stack (cpu related)
+ *   - the synchronous kernel stack (process related)
+ * The stack trace can start at any of the three stack and can potentially
+ * touch all of them. The order is: panic stack, async stack, sync stack.
+ */
+static unsigned long
+__show_trace(unsigned long sp, unsigned long low, unsigned long high)
+{
+       struct stack_frame *sf;
+       struct pt_regs *regs;
+
+       while (1) {
+               sp = sp & PSW_ADDR_INSN;
+               if (sp < low || sp > high - sizeof(*sf))
+                       return sp;
+               sf = (struct stack_frame *) sp;
+               printk("([<%016lx>] ", sf->gprs[8] & PSW_ADDR_INSN);
+               print_symbol("%s)\n", sf->gprs[8] & PSW_ADDR_INSN);
+               /* Follow the backchain. */
+               while (1) {
+                       low = sp;
+                       sp = sf->back_chain & PSW_ADDR_INSN;
+                       if (!sp)
+                               break;
+                       if (sp <= low || sp > high - sizeof(*sf))
+                               return sp;
+                       sf = (struct stack_frame *) sp;
+                       printk(" [<%016lx>] ", sf->gprs[8] & PSW_ADDR_INSN);
+                       print_symbol("%s\n", sf->gprs[8] & PSW_ADDR_INSN);
+               }
+               /* Zero backchain detected, check for interrupt frame. */
+               sp = (unsigned long) (sf + 1);
+               if (sp <= low || sp > high - sizeof(*regs))
+                       return sp;
+               regs = (struct pt_regs *) sp;
+               printk(" [<%016lx>] ", regs->psw.addr & PSW_ADDR_INSN);
+               print_symbol("%s\n", regs->psw.addr & PSW_ADDR_INSN);
+               low = sp;
+               sp = regs->gprs[15];
+       }
+}
+
+static void show_trace(struct task_struct *task, unsigned long *stack)
+{
+       register unsigned long __r15 asm ("15");
+       unsigned long sp;
+
+       sp = (unsigned long) stack;
+       if (!sp)
+               sp = task ? task->thread.ksp : __r15;
+       printk("Call Trace:\n");
+#ifdef CONFIG_CHECK_STACK
+       sp = __show_trace(sp, S390_lowcore.panic_stack - 4096,
+                         S390_lowcore.panic_stack);
+#endif
+       sp = __show_trace(sp, S390_lowcore.async_stack - ASYNC_SIZE,
+                         S390_lowcore.async_stack);
+       if (task)
+               __show_trace(sp, (unsigned long) task_stack_page(task),
+                            (unsigned long) task_stack_page(task) + THREAD_SIZE);
+       else
+               __show_trace(sp, S390_lowcore.thread_info,
+                            S390_lowcore.thread_info + THREAD_SIZE);
+       if (!task)
+               task = current;
+       debug_show_held_locks(task);
+}
+
+void show_stack(struct task_struct *task, unsigned long *sp)
+{
+       register unsigned long *__r15 asm ("15");
+       unsigned long *stack;
+       int i;
+
+       if (!sp)
+               stack = task ? (unsigned long *) task->thread.ksp : __r15;
+       else
+               stack = sp;
+
+       for (i = 0; i < kstack_depth_to_print; i++) {
+               if (((addr_t) stack & (THREAD_SIZE-1)) == 0)
+                       break;
+               if ((i * sizeof(long) % 32) == 0)
+                       printk("%s       ", i == 0 ? "" : "\n");
+               printk(LONG, *stack++);
+       }
+       printk("\n");
+       show_trace(task, sp);
+}
+
+static void show_last_breaking_event(struct pt_regs *regs)
+{
+#ifdef CONFIG_64BIT
+       printk("Last Breaking-Event-Address:\n");
+       printk(" [<%016lx>] ", regs->args[0] & PSW_ADDR_INSN);
+       print_symbol("%s\n", regs->args[0] & PSW_ADDR_INSN);
+#endif
+}
+
+/*
+ * The architecture-independent dump_stack generator
+ */
+void dump_stack(void)
+{
+       printk("CPU: %d %s %s %.*s\n",
+              task_thread_info(current)->cpu, print_tainted(),
+              init_utsname()->release,
+              (int)strcspn(init_utsname()->version, " "),
+              init_utsname()->version);
+       printk("Process %s (pid: %d, task: %p, ksp: %p)\n",
+              current->comm, current->pid, current,
+              (void *) current->thread.ksp);
+       show_stack(NULL, NULL);
+}
+EXPORT_SYMBOL(dump_stack);
+
+static inline int mask_bits(struct pt_regs *regs, unsigned long bits)
+{
+       return (regs->psw.mask & bits) / ((~bits + 1) & bits);
+}
+
+void show_registers(struct pt_regs *regs)
+{
+       char *mode;
+
+       mode = user_mode(regs) ? "User" : "Krnl";
+       printk("%s PSW : %p %p",
+              mode, (void *) regs->psw.mask,
+              (void *) regs->psw.addr);
+       print_symbol(" (%s)\n", regs->psw.addr & PSW_ADDR_INSN);
+       printk("           R:%x T:%x IO:%x EX:%x Key:%x M:%x W:%x "
+              "P:%x AS:%x CC:%x PM:%x", mask_bits(regs, PSW_MASK_PER),
+              mask_bits(regs, PSW_MASK_DAT), mask_bits(regs, PSW_MASK_IO),
+              mask_bits(regs, PSW_MASK_EXT), mask_bits(regs, PSW_MASK_KEY),
+              mask_bits(regs, PSW_MASK_MCHECK), mask_bits(regs, PSW_MASK_WAIT),
+              mask_bits(regs, PSW_MASK_PSTATE), mask_bits(regs, PSW_MASK_ASC),
+              mask_bits(regs, PSW_MASK_CC), mask_bits(regs, PSW_MASK_PM));
+#ifdef CONFIG_64BIT
+       printk(" EA:%x", mask_bits(regs, PSW_MASK_EA | PSW_MASK_BA));
+#endif
+       printk("\n%s GPRS: " FOURLONG, mode,
+              regs->gprs[0], regs->gprs[1], regs->gprs[2], regs->gprs[3]);
+       printk("           " FOURLONG,
+              regs->gprs[4], regs->gprs[5], regs->gprs[6], regs->gprs[7]);
+       printk("           " FOURLONG,
+              regs->gprs[8], regs->gprs[9], regs->gprs[10], regs->gprs[11]);
+       printk("           " FOURLONG,
+              regs->gprs[12], regs->gprs[13], regs->gprs[14], regs->gprs[15]);
+       show_code(regs);
+}
+
+void show_regs(struct pt_regs *regs)
+{
+       printk("CPU: %d %s %s %.*s\n",
+              task_thread_info(current)->cpu, print_tainted(),
+              init_utsname()->release,
+              (int)strcspn(init_utsname()->version, " "),
+              init_utsname()->version);
+       printk("Process %s (pid: %d, task: %p, ksp: %p)\n",
+              current->comm, current->pid, current,
+              (void *) current->thread.ksp);
+       show_registers(regs);
+       /* Show stack backtrace if pt_regs is from kernel mode */
+       if (!user_mode(regs))
+               show_trace(NULL, (unsigned long *) regs->gprs[15]);
+       show_last_breaking_event(regs);
+}
+
+static DEFINE_SPINLOCK(die_lock);
+
+void die(struct pt_regs *regs, const char *str)
+{
+       static int die_counter;
+
+       oops_enter();
+       lgr_info_log();
+       debug_stop_all();
+       console_verbose();
+       spin_lock_irq(&die_lock);
+       bust_spinlocks(1);
+       printk("%s: %04x [#%d] ", str, regs->int_code & 0xffff, ++die_counter);
+#ifdef CONFIG_PREEMPT
+       printk("PREEMPT ");
+#endif
+#ifdef CONFIG_SMP
+       printk("SMP ");
+#endif
+#ifdef CONFIG_DEBUG_PAGEALLOC
+       printk("DEBUG_PAGEALLOC");
+#endif
+       printk("\n");
+       notify_die(DIE_OOPS, str, regs, 0, regs->int_code & 0xffff, SIGSEGV);
+       print_modules();
+       show_regs(regs);
+       bust_spinlocks(0);
+       add_taint(TAINT_DIE, LOCKDEP_NOW_UNRELIABLE);
+       spin_unlock_irq(&die_lock);
+       if (in_interrupt())
+               panic("Fatal exception in interrupt");
+       if (panic_on_oops)
+               panic("Fatal exception: panic_on_oops");
+       oops_exit();
+       do_exit(SIGSEGV);
+}
index 13dd63fba367e1ccd7b113f4ad2a6ebf25af7845..c5762324d9ee435367314d8fa2f03e32e2365f0e 100644 (file)
  * 'Traps.c' handles hardware traps and faults after we have saved some
  * state in 'asm.s'.
  */
-#include <linux/sched.h>
-#include <linux/kernel.h>
-#include <linux/string.h>
-#include <linux/errno.h>
+#include <linux/kprobes.h>
+#include <linux/kdebug.h>
+#include <linux/module.h>
 #include <linux/ptrace.h>
-#include <linux/timer.h>
+#include <linux/sched.h>
 #include <linux/mm.h>
-#include <linux/smp.h>
-#include <linux/init.h>
-#include <linux/interrupt.h>
-#include <linux/seq_file.h>
-#include <linux/delay.h>
-#include <linux/module.h>
-#include <linux/kdebug.h>
-#include <linux/kallsyms.h>
-#include <linux/reboot.h>
-#include <linux/kprobes.h>
-#include <linux/bug.h>
-#include <linux/utsname.h>
-#include <asm/uaccess.h>
-#include <asm/io.h>
-#include <linux/atomic.h>
-#include <asm/mathemu.h>
-#include <asm/cpcmd.h>
-#include <asm/lowcore.h>
-#include <asm/debug.h>
-#include <asm/ipl.h>
 #include "entry.h"
 
 int show_unhandled_signals = 1;
 
-#define stack_pointer ({ void **sp; asm("la %0,0(15)" : "=&d" (sp)); sp; })
-
-#ifndef CONFIG_64BIT
-#define LONG "%08lx "
-#define FOURLONG "%08lx %08lx %08lx %08lx\n"
-static int kstack_depth_to_print = 12;
-#else /* CONFIG_64BIT */
-#define LONG "%016lx "
-#define FOURLONG "%016lx %016lx %016lx %016lx\n"
-static int kstack_depth_to_print = 20;
-#endif /* CONFIG_64BIT */
-
 static inline void __user *get_trap_ip(struct pt_regs *regs)
 {
 #ifdef CONFIG_64BIT
@@ -72,215 +39,6 @@ static inline void __user *get_trap_ip(struct pt_regs *regs)
 #endif
 }
 
-/*
- * For show_trace we have tree different stack to consider:
- *   - the panic stack which is used if the kernel stack has overflown
- *   - the asynchronous interrupt stack (cpu related)
- *   - the synchronous kernel stack (process related)
- * The stack trace can start at any of the three stack and can potentially
- * touch all of them. The order is: panic stack, async stack, sync stack.
- */
-static unsigned long
-__show_trace(unsigned long sp, unsigned long low, unsigned long high)
-{
-       struct stack_frame *sf;
-       struct pt_regs *regs;
-
-       while (1) {
-               sp = sp & PSW_ADDR_INSN;
-               if (sp < low || sp > high - sizeof(*sf))
-                       return sp;
-               sf = (struct stack_frame *) sp;
-               printk("([<%016lx>] ", sf->gprs[8] & PSW_ADDR_INSN);
-               print_symbol("%s)\n", sf->gprs[8] & PSW_ADDR_INSN);
-               /* Follow the backchain. */
-               while (1) {
-                       low = sp;
-                       sp = sf->back_chain & PSW_ADDR_INSN;
-                       if (!sp)
-                               break;
-                       if (sp <= low || sp > high - sizeof(*sf))
-                               return sp;
-                       sf = (struct stack_frame *) sp;
-                       printk(" [<%016lx>] ", sf->gprs[8] & PSW_ADDR_INSN);
-                       print_symbol("%s\n", sf->gprs[8] & PSW_ADDR_INSN);
-               }
-               /* Zero backchain detected, check for interrupt frame. */
-               sp = (unsigned long) (sf + 1);
-               if (sp <= low || sp > high - sizeof(*regs))
-                       return sp;
-               regs = (struct pt_regs *) sp;
-               printk(" [<%016lx>] ", regs->psw.addr & PSW_ADDR_INSN);
-               print_symbol("%s\n", regs->psw.addr & PSW_ADDR_INSN);
-               low = sp;
-               sp = regs->gprs[15];
-       }
-}
-
-static void show_trace(struct task_struct *task, unsigned long *stack)
-{
-       register unsigned long __r15 asm ("15");
-       unsigned long sp;
-
-       sp = (unsigned long) stack;
-       if (!sp)
-               sp = task ? task->thread.ksp : __r15;
-       printk("Call Trace:\n");
-#ifdef CONFIG_CHECK_STACK
-       sp = __show_trace(sp, S390_lowcore.panic_stack - 4096,
-                         S390_lowcore.panic_stack);
-#endif
-       sp = __show_trace(sp, S390_lowcore.async_stack - ASYNC_SIZE,
-                         S390_lowcore.async_stack);
-       if (task)
-               __show_trace(sp, (unsigned long) task_stack_page(task),
-                            (unsigned long) task_stack_page(task) + THREAD_SIZE);
-       else
-               __show_trace(sp, S390_lowcore.thread_info,
-                            S390_lowcore.thread_info + THREAD_SIZE);
-       if (!task)
-               task = current;
-       debug_show_held_locks(task);
-}
-
-void show_stack(struct task_struct *task, unsigned long *sp)
-{
-       register unsigned long * __r15 asm ("15");
-       unsigned long *stack;
-       int i;
-
-       if (!sp)
-               stack = task ? (unsigned long *) task->thread.ksp : __r15;
-       else
-               stack = sp;
-
-       for (i = 0; i < kstack_depth_to_print; i++) {
-               if (((addr_t) stack & (THREAD_SIZE-1)) == 0)
-                       break;
-               if ((i * sizeof(long) % 32) == 0)
-                       printk("%s       ", i == 0 ? "" : "\n");
-               printk(LONG, *stack++);
-       }
-       printk("\n");
-       show_trace(task, sp);
-}
-
-static void show_last_breaking_event(struct pt_regs *regs)
-{
-#ifdef CONFIG_64BIT
-       printk("Last Breaking-Event-Address:\n");
-       printk(" [<%016lx>] ", regs->args[0] & PSW_ADDR_INSN);
-       print_symbol("%s\n", regs->args[0] & PSW_ADDR_INSN);
-#endif
-}
-
-/*
- * The architecture-independent dump_stack generator
- */
-void dump_stack(void)
-{
-       printk("CPU: %d %s %s %.*s\n",
-              task_thread_info(current)->cpu, print_tainted(),
-              init_utsname()->release,
-              (int)strcspn(init_utsname()->version, " "),
-              init_utsname()->version);
-       printk("Process %s (pid: %d, task: %p, ksp: %p)\n",
-              current->comm, current->pid, current,
-              (void *) current->thread.ksp);
-       show_stack(NULL, NULL);
-}
-EXPORT_SYMBOL(dump_stack);
-
-static inline int mask_bits(struct pt_regs *regs, unsigned long bits)
-{
-       return (regs->psw.mask & bits) / ((~bits + 1) & bits);
-}
-
-void show_registers(struct pt_regs *regs)
-{
-       char *mode;
-
-       mode = user_mode(regs) ? "User" : "Krnl";
-       printk("%s PSW : %p %p",
-              mode, (void *) regs->psw.mask,
-              (void *) regs->psw.addr);
-       print_symbol(" (%s)\n", regs->psw.addr & PSW_ADDR_INSN);
-       printk("           R:%x T:%x IO:%x EX:%x Key:%x M:%x W:%x "
-              "P:%x AS:%x CC:%x PM:%x", mask_bits(regs, PSW_MASK_PER),
-              mask_bits(regs, PSW_MASK_DAT), mask_bits(regs, PSW_MASK_IO),
-              mask_bits(regs, PSW_MASK_EXT), mask_bits(regs, PSW_MASK_KEY),
-              mask_bits(regs, PSW_MASK_MCHECK), mask_bits(regs, PSW_MASK_WAIT),
-              mask_bits(regs, PSW_MASK_PSTATE), mask_bits(regs, PSW_MASK_ASC),
-              mask_bits(regs, PSW_MASK_CC), mask_bits(regs, PSW_MASK_PM));
-#ifdef CONFIG_64BIT
-       printk(" EA:%x", mask_bits(regs, PSW_MASK_EA | PSW_MASK_BA));
-#endif
-       printk("\n%s GPRS: " FOURLONG, mode,
-              regs->gprs[0], regs->gprs[1], regs->gprs[2], regs->gprs[3]);
-       printk("           " FOURLONG,
-              regs->gprs[4], regs->gprs[5], regs->gprs[6], regs->gprs[7]);
-       printk("           " FOURLONG,
-              regs->gprs[8], regs->gprs[9], regs->gprs[10], regs->gprs[11]);
-       printk("           " FOURLONG,
-              regs->gprs[12], regs->gprs[13], regs->gprs[14], regs->gprs[15]);
-
-       show_code(regs);
-}      
-
-void show_regs(struct pt_regs *regs)
-{
-       printk("CPU: %d %s %s %.*s\n",
-              task_thread_info(current)->cpu, print_tainted(),
-              init_utsname()->release,
-              (int)strcspn(init_utsname()->version, " "),
-              init_utsname()->version);
-       printk("Process %s (pid: %d, task: %p, ksp: %p)\n",
-              current->comm, current->pid, current,
-              (void *) current->thread.ksp);
-       show_registers(regs);
-       /* Show stack backtrace if pt_regs is from kernel mode */
-       if (!user_mode(regs))
-               show_trace(NULL, (unsigned long *) regs->gprs[15]);
-       show_last_breaking_event(regs);
-}
-
-static DEFINE_SPINLOCK(die_lock);
-
-void die(struct pt_regs *regs, const char *str)
-{
-       static int die_counter;
-
-       oops_enter();
-       lgr_info_log();
-       debug_stop_all();
-       console_verbose();
-       spin_lock_irq(&die_lock);
-       bust_spinlocks(1);
-       printk("%s: %04x [#%d] ", str, regs->int_code & 0xffff, ++die_counter);
-#ifdef CONFIG_PREEMPT
-       printk("PREEMPT ");
-#endif
-#ifdef CONFIG_SMP
-       printk("SMP ");
-#endif
-#ifdef CONFIG_DEBUG_PAGEALLOC
-       printk("DEBUG_PAGEALLOC");
-#endif
-       printk("\n");
-       notify_die(DIE_OOPS, str, regs, 0, regs->int_code & 0xffff, SIGSEGV);
-       print_modules();
-       show_regs(regs);
-       bust_spinlocks(0);
-       add_taint(TAINT_DIE, LOCKDEP_NOW_UNRELIABLE);
-       spin_unlock_irq(&die_lock);
-       if (in_interrupt())
-               panic("Fatal exception in interrupt");
-       if (panic_on_oops)
-               panic("Fatal exception: panic_on_oops");
-       oops_exit();
-       do_exit(SIGSEGV);
-}
-
 static inline void report_user_fault(struct pt_regs *regs, int signr)
 {
        if ((task_pid_nr(current) > 1) && !show_unhandled_signals)